This invention relates to a novel process for detection of leaky seals in containers and apparatus for carrying out this process. The invention is related particularly to detecting leaks in packages having a flexible lid material sealed to a container body such that the resulting seal structure forms a flange-like structure on the sealed package.
Many leak-detecting machines have been suggested over the years. Some such machines utilize some method of infusing air into a leaky container. One such Pat. No. 4,326,408 to Kanoh describes how leakage of air into a watchcase is detected. Most such apparatus, however, is used in packaging food or other objects which are sealed in sterile packages. Thus U.S. Pat. Nos. 2,093,429 to Foss; 3,751,972 to Hass; and 1,974,026 to Hicks show methods of testing cans. Proximity sensors are known for use in detecting movement of a container wall as seen in U.S. Pat. No. 4,188,819. More recently Wyslotsky et al, in U.S. Pat. No. 4,409,818 utilizes displacement sensors to detect air blown through defective seals between two plastic sheets (one a container structure, the other a lid structure) of a package.
It will be evident that the Wyslotsky device depends upon the availability of unsealed package area for effective containment of test gases. Moreover, it will be noted that Wyslotsky's test pressure exerts a significant pull on the package webs and thereby tends to pull a seal open. This limits somewhat the strength of seal utilized with that apparatus.